If (x) and f-1 (x) are inverse functions of each other and f (X) = 2X+5 what is f-1 (8)

F (x) = 2x+5

We can rewrite as y = 2x + 5.

We need to find x.

y=2x+5

y-5 = 2x

x = (y-5) / 2

Now we need exchange y by x, and x by y.

x = (y-5) / 2

y = (x-5) / 2

f⁻¹ (x) = (x-5) / 2

f⁻¹ (8) = (8-5) / 2 = 3/2 = 1.5

f⁻¹ (8) = 3/2 or f⁻¹ (8) = 1.5